Status of BESIII and upgrade of BESIII Ming
Status of BESIII and upgrade of BESIII Ming Shao / USTC for the BES Collaboration 1
Outline • • Commissioning of BEPCII/BESIII Performance of the BESIII detector Upgrade of BESIII Summary 2
BEPC II Storage ring: Large angle, double-ring RF SR RF Beam energy: 1. 0 -2. 3 Ge. V Luminosity: 1× 1033 cm-2 s-1 Optimum energy: 1. 89 Ge. V Energy spread: 5. 16 × 10 -4 No. of bunches: 93 Bunch length: 1. 5 cm Total current: 0. 91 A SR mode: 0. 25 A @ 2. 5 Ge. V IP 3
Main parameters achieved in collision mode parameters design Energy (Ge. V) 1. 89 Beam curr. (m. A) 910 650 700 Bunch curr. (m. A) 9. 8 >10 Bunch number 93 93 93 RF voltage 1. 5 0. 033 0. 032 1. 0/0. 015 ~1. 0/0. 016 Inj. Rate (m. A/min) 200 e-/ 50 e+ >200 >50 Lum. (1033 cm-2 s-1) 1 *ns @1. 5 MV x*/ y* (m) Achieved BER BPR 0. 30 4
BESIII detector Magnet yoke SC magnet, 1 T RPC MUC TOF, (barrel) 90/ (endcap)110~120 ps Be beam pipe MDC, 130 mm Cs. I(Tl) calorimeter, 2. 5%@1 Ge. V 5
First collision event on July 19, 2008 14 M ’ events collected in 2008 6
Drift chamber • To measure the momentum of charged particles by their curvature in the magnetic field • • 7000 Signal wires: 25 mm gold-plated tungsten 22000 Field wires: 110 mm Al Gas: He + C 3 H 8 (60/40) Momentum resolution@1 Ge. V: Babar: ~ 110 mm BELLE: ~ 130 mm CLEO: ~ 110 mm BESIII: ~ 130 mm 7
MDC calibration Reso. 136 mm Eff. : ~ 98% Beam related backgrounds Wire reso. ● ● Layer 7 Layer 22 σP=13. 7 Me. V/c 8
d. E/dx resolution d. E/dx reso. : 5. 80% K p 9
BESIII Cs. I(Tl) crystal calorimeter • • To measure the energy of electromagnetic particles Barrel: 5280 crystals,Endcap: 960 crystals Babar: 2. 67%@1 Ge. V Crystal: (5. 2 x 5. 2 – 6. 4 x 6. 4) x 28 cm 3 BELLE: 2. 2% @1 Ge. V Readout: 13000 Photodiodes, 1 cm 2 cm, CLEO: 2. 2% @1 Ge. V Energy range: 20 Me. V – 2 Ge. V position resolution: 6 mm @ 1 Ge. V BESIII: 2. 5%@1 Ge. V Tilt angle: theta ~ 1 -3 o, phi ~ 1. 5 o 10
EMC calibration Barrel energy resolution for Bhabha events energy deposit for e+e- gg Position resolution for Bhabha 4. 4 mm 11
PID: TOF system • Barrel: 2*88 BC 408, 2. 4 m long, 5 cm thick • Endcap: 2*48 BC 404 • PMT: Hamamatzu R 5924 experiment lengt(cm) Intrinsic resolution BESIII 240 90 ps CLEOII 280 139 ps OBELIX 300 170 ps BELLE 255 90~100 ps CDFII 279 100 ps HARP 180 -250 160 ps 12
TOF calibration TOF Barrel: 103 ps Design: 100~110 ps (single layer) Endcap TOF: 125 ps Design: 110~120 ps 13
m system : RPC • • 9 layer, 2000 m 2 Special bakelite plate w/o lineseed oil 4 cm strips, 10000 channels Noise less than 0. 1 Hz/cm 2 14
MUON Chamber Efficiency Spatial resolution Single counting rate 15
BESIII commissioning and data taking milestones Mar. 2008: first full cosmic-ray event April 30, 2008: Move the BESIII to IP July 20, 2008: First e+e- collision event in BESIII Nov. 2008: ~ 14 M (2 S) events collected April 14, 2009 ~100 M (2 S) events collected May 30, 2009 ~42 pb-1 at continuum collected (3. 65 Ge. V) July 28, 2009 ~200 M J/ events collected Peak Lumi. @ Nov. 2008: 1. 2 1032 cm-2 s-1 Peak Lumi. @ May 2009: 3. 2 1032 cm-2 s-1 16
Data accumulated at BESIII Mar. 6 – April 14 100 M (2 S) data May 24 – June 2 42 pb-1 data at 3. 65 Ge. V June 12 – Jul. 28 200 M J/ data 17
Upgrade of BESIII TOF ! ΔT>3. 38 σ separation rate >95. 4%(2σ) ΔT>5. 60 σ separation rate >99. 7%(3σ) Current time resolution can separate kaon/pion of <0. 95 Ge. V/c in the middle of barrel We aim at 1. 1 -1. 2 Ge. V/c 18
Time resolution in BESIII/TOF Non TOF ~60 ps Upgrade ! Item Barrel time reso. Endcap time reso. Intrinsic time reso. of one TOF layer for 1 Ge. V muon 80~90 ps 80 ps Uncertainty from electronics 25 ps Uncertainty from bunch length 15 mm,35 ps Uncertainty from bunch time ~20 ps Uncertainty from Z position 5 mm, 25 ps 10 mm, 50 ps Resolution of expected time of flight 30 ps Total time reso, one layer of TOF for 1 Ge. V muon 100~110 ps 110~120 ps Total time reso, double layer of TOF for 1 Ge. V muon 90 ps Target: Intrinsic time resolution < 45 ps, Total time resolution < 72 ps, corresponding to a K/pi separation capability up to >1. 1 Ge. V (95%C. L. ). 19
TOF Technique - MRPC A 24 gaps Timing MRPC 20
Beam Test at T 10 Efficiency (%) Time resolution (ps) HV (k. V) Time distribution (ps) Signal width – TOT (ns) 21
Schematic view of MRPC TOF barrel endcap 22
Summary • BEPCII achieved a luminosity of 3 1032 cm-2 s-1 • The performance of the BESIII detector reached expectations • 100 M ’ , 200 M J/ events have been accumulated; the data quality is good & preliminary results are being obtained • We are expecting exciting physics results • Upgrade of BESIII is undergoing Thank you ! 23
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EMC installation 25
MDC and TOF installation 26
Be Beam-pipe installation 27
BESIII moved to IP: precision < 1 mm 28
MDC Data/MC comparison • Detailed simulation: • Resolution/efficiency of each cell as a function of drift distance, DOCA, Q, HV, Noise, entrance angle, … • Improvements: more data, better understanding, … 29
Very low electronics noise (EMC) 30
EMC Data/MC comparison for Bhabha events Dots: data Solid line: MC with background mixing Dash line/shade: MC without background mixing 31
EMC Data/MC comparison e- e+ + p 32
Summary of BESIII performance Wire reso. Design: 130 mm ● ● d. E/dx reso. : 5. 80% Design: 6 -8% Layer 7 Layer 22 Cs. I(Tl) energy reso. Design: 2. 5%@ 1 Ge. V Bhabha Barrel TOF reso. : 78 ps Design: 90 ps 33
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